The purpose of this proposal is to demonstrate the capabilities and the willingness of the University of Pittsburgh to participate in a multicenter, cooperative network with other Maternal-Fetal Medicine units. The University of Pittsburgh is staffed by 6 specialists in Maternal-Fetal Medicine whose published research interests include preterm delivery, tocolytic agents, infectious disease, ultrasound, fetal physiology and surveillance, fetal growth and diabetes. The obstetrical unit of the University of Pittsburgh is the largest private obstetrical service in the United States with more than 10,000 annual deliveries. More than 3000 patients are high risk, approximately 1000 have medical complications of pregnancy, 2300 are indigent and about 1600 are black or hispanic. In addition, approximately 350 pregnant women with medical or obstetrical complications are transferred from other hospitals to our facility annually for obstetrical care. We propose a project for the network that is based on our unique research experience and our belief that the area of greatest importance in obstetrics today is preterm labor. Ritodrine is the only drug approved for the treatment of preterm labor but because kinetic studies were not performed in pregnant women prior to the drug's approval, serious deficiencies in efficacy and safety have become apparent. With the current infusion regimen, as many as 9% of women receiving ritodrine develop pulmonary edema, 18% have chest pain, 20% vomit, 18% have shortness of breath, 50% have a diastolic pressure less than 40 mmHg and 60% have a heart rate in excess of 130 beats per minute. We propose a two-step study to improve the safety of ritodrine. First, we will define the kinetic behavior of ritodrine in 30 pregnant women who are receiving ritodrine for preterm labor. We will use the kinetic data to define infusion regimens that minimize the likelihood of drug overdose. We will then conduct a prospective randomized study in 260 women in preterm labor to compare the incidence of side effects with the infusion regimen recommended by the manufacturer and the kinetically-based regimen.